The pelvis

Information

The pelvis is the bowl-shaped structure generated by the two coxal bones articulated with the sacrum and coccyx bones. On the anterior side of the pelvis, the pubis portions of the two coxal bones do not articulate with each other, but instead are joined with a small piece of cartilage called the pubic symphysis (“PYOO-bick SIM-fiss-is”)

Figure 7-15. The bones of the pelvis.

 

Anatomists divide the pelvis into two regions. The false pelvis is superior and is surrounded by iliac fossa portions of the coxal bones and the upper portion of the sacrum. The true pelvis is inferior and is surrounded by the pubis and ischium portions of the coxal bones, in addition to the lower sections of the ilium and the sacrum. In women, the true pelvis defines the space babies must squeeze through during childbirth.

Figure 7-16. The true pelvis vs. the false pelvis.

 

One of the few ways a skeleton stripped of all flesh can be reliably established as either male or female comes from examining the pelvis. The female pelvis can be distinguished from the male pelvis by a number or criterion, three of which are shown in Figure 7-17.

Most of these anatomical differences between the pelvises of males and females reflect the fact that only female pelvises have to serve as part of the birth canal, and these sex differences are not as pronounced in the skeletons of children who have not finished puberty.

In female pelvises, both the pelvic inlet and the pelvic outlet (not shown in Figure 7-17) are wider and more oval-shaped than those in male pelvises. The pelvic inlet in males tends to be more heart-shaped (narrower on the dorsal side) and the pelvic outlet tends to be more narrow. The pubic arch, found immediately inferior to the pubic symphysis, tends to form an angle closer to 90° in females, but forms an angle closer to 60° in males. The sacrum in female pelvises tends to be less curved; in male pelvises, the sacrum is more curved and tends to impinge upon the space of the pubic outlet.

Figure 7-17. Major differences that distinguish the adult male pelvis from the adult female pelvis.

 

LAb 7 exercises 7.5

  1. There will be an intact pelvis set up at the instructor’s station. Using the criteria in Figure 7-17 determine if the pelvis came from a male or female. Give three lines of evidence to support your conclusion.
Male or female?
Evidence 1.                                                                                                        .
Evidence 2.
Evidence 3.